Examinando por Autor "Seoane, Carlos"

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Highly efficient solution-processed white organic light-emitting diodes based on novel copolymer single layer
(Elsevier, 2012) Coya, Carmen; Álvarez, Ángel Luis; Ramos, Mar; Gómez, Rafael; Seoane, Carlos; Segura, José Luis
We fabricate by solution processed methods organic light emitting diodes with single-layer structure (ITO/(PEDOT:PSS)/co-polymer/Ba/Al) and study the transport properties of the final devices. The copolymer is novel poly(fluorene-alt-phenylene) (PFP) derivatives containing co-monomers, involving red-emitting 1,8-naphthalimide units as pendant groups (0.0005, 0.005, 0.02 and 0.08 wt%) covalently attached. All the devices exhibited emission at very low driving currents in the A range (47¿73 A). White emission with luminous efficiency of 9.42 Cd/A at 50 A is obtained for the co-polymer with the smallest amount of chromophore. Commission Internationale de L¿Eclairage (CIE) coordinates evolve from almost pure white color (0.26, 0.30) for low currents to stable cool white (0.21, 0.23). Increasing naphthalimide contents leads to stable green and orange emission with 3.07, 19.5 and 6.7 Cd/A efficiencies. The current-voltage response of the devices is analyzed by means of a numerical model that includes an injection mechanism based in the microscopic hopping theory and a field-dependent carrier mobility for the bulk transport regime. The fitting results allow to estimate the dependence of carrier mobility on polymer composition in the diodes.
Synthesis and electrochemical characterization of donor-acceptor phenylazomethine dendrimers
(ELSEVIER, 2005-12) Juárez, Rafael; Gómez, Rafael; Segura, José L.; Seoane, Carlos
The synthesis of the first donor-acceptor phenylazomethine dendrimers (4 and 5) is described. A convergent method is used via the condensation of aromatic ketones with an appropriately functionalized tri(aminophenyl)-s-triazine promoted by titanium (IV) chloride. Cyclic voltammetry investigations show a donor-acceptor behaviour due to the presence of the electron acceptor s-triazine core and the donor ability of the conjugated peripheral butoxybenzene units.
Synthesis and tunable emission of novel polyfluorene co-polymers with 1,8-naphthalimide pendant groups and application in a single layer-single component white emitting device
(ELSEVIER, 2010-08) Juárez, Rafael; Coya, Carmen; Blanco, Raúl; Gómez, Rafael; Martínez, Rocío; Andrés, Alicia de; Álvarez, Ángel Luis; Zaldo, Carlos; Ramos, María M.; Peña, Alejandro de la; Seoane, Carlos; Segura, José L.
New luminescent polymers containing two individual emission species-poly(fluorene-alt-phenylene) as a blue host and variable amounts of 1,8-naphthalimide as red dopant have been designed and synthesized. Optical studies (optical absorption (OA) and steady-state photoluminescence emission (PL)) in diluted solutions and thin solid films reveal that the emission spectrum can be tuned by varying the content of 1,8-naphthalimide moieties. Although no significant interaction can be observed between both moieties in the ground state, after photoexcitation an efficient energy transfer takes place from the PFP backbone to the red chromophore, indeed, by adjusting the polymer/naphthalimide ratio it is possible to obtain single polymers which emit white light to the human eye in solid state. Energy transfer is more effective in the co-polymers than in physical mixtures of the two chromophores. We prepared single-layer electroluminescent simple devices with structure: ITO/poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT:PSS)/active layer/Ba/Al. With this single layer¿single component device structure, white light with Commission Internationale de l¿Eclairage (CIE) color coordinates (0.3, 0.42) is obtained for the electroluminescence (EL) emission with an efficiency of 22.62 Cd/A.